The starting material for the production of active-mass is lead powder. Lead powder is prepared from lead, e.g. in a Barton mill usually known in the industry, and in the course of milling, depending on the grinding conditions, lead oxide is also formed in different ratios.
The powder thus obtained is subjected to sulfuric acid/phoshoric acid treatment, depending on whether positive or negative active-mass is aimed to be prepared, and additives, e.g. sulfuric acid, barium sulfate, carbon black, are mixed to the product thus obtained. The resulting crude active-mass is spread onto electrodes of grid structure with the aid of a spreading machine. Then further operations are carried out on the mass thus applied onto the plates, e.g. pre-drying and aging. Finally the plates are placed into containers, wherein optionally the appropriate polarities are bound together, then the containers are filled with an acid and then closed.
In the accumulator production a certain amount of defective product is also produced, the accumulators are consumed during operation, they become unserviceable and sooner or later they are deposited in rubbish-shoots.
Therefore, the need for the reprocessing of unserviceable accumulators, especially of their most expensive and poisonous lead plates and masses, and the recycling of the same into the current production, exists for a long time. According to the most wide-spread method the accumulators are dismantled, washed, etc. and subjected to metallurgical treatment, i.e. the lead alloy of the plate grid is melted, then a grid is formed from the melt.
Several processes are known for the re-use of the negative active-mass content of waste plates. According to U.S. patent specification Ser. No. 4,009,833 the separated active-mass is recycled into the mixing machines. This process is more economic than the multistep chemical method when the active-mass is separated into its components by a wet chemical method but this method can be used only for the working up of negative active-mass waste.
The common disadvantages of the known processes are the high energy- and water demand, low efficacy, health hazard and environment pollution.
In the course of production wastes are also formed e.g. when spreading the active-mass onto the grid, while drying and during formation of the plates, etc. The working up of the said waste is described in Hungarian patent specification Ser. No. 201,179.
The aim of our experiments and examinations was to find a simple process for the recycling of waste positive and negative active-masses separated from the consumed, industrially operated, broken accumulator plates deriving from rubbish-shoots, i.e. not from the factory, into the active-mass production in a simple way, without causing any deterioration in quality of the accumulators being the end-products of the process.
The invention is based on the recognition that the above aim can be achieved if the negative and positive active-masses deriving from consumed, broken, unserviceable accumulators of rubbish-shoots are washed acid-free, appropriately ground and subjected to a special heat-treatment. The quality of the accumulators assembled with the thus-obtained active-mass is equal to that of accumulators assembled with fresh active-mass.
The invention is based on the further recognition that the mixture of waste positive and negative active-masses can be worked up into negative active-mass of good quality. This recognition is surprising as it overcomes a technical prejudice. Namely, formerly it was an accepted view of persons skilled in the art that if production-refuse active-mass is used as starting material, negative active-mass of suitable quality can be prepared only from separately stored and treated negative active-mass waste (Hungarian patent specification No. 201,179).